I returned an iphone 4 today to my local Apple store because of a piece of particulate matter that was under the outer glass that covers the camera lens. The problem was easily verified and I was given a replacement unit. The replacement unit has the same type of defect. Of course the piece of paticulate is different in appearance than that of the first unit; unfortunately, this one is a bit larger and is either in the glass itself or stuck to the underneath very near the center. Just curious if this has been an issue for any of you folks. Thanks.